Students study the rates of evaporation of different liquids. Take four identical bowls and add 1/2 liter of the following to them: tap water, tap water with 2 tbsp. salt, vinegar and rubbing alcohol. Weigh each bowl. Place the bowls next to one another on a windowsill that receives plenty of natural light. Start a timer. Take photographs of your experiment setup, as this will be useful for any future presentation at a science fair. Weigh your bowls every two hours, noting any differences. Continue your experiment for at least eight hours before determining which liquid evaporated fastest and graphing your results. Rubbing alcohol evaporates fastest, vinegar second fastest and water and salt water the slowest, at roughly the same rate, because water and salt water have more hydrogen bonding than the other two.
Take two identical shoeboxes, discard their lids and put about 1 inch of potting soil in each box. Weigh each box and add soil where necessary until they are identical in weight. Lay a thermometer flat in the middle of the soil so you can take a reading by looking into the shoebox from a standing position. Wrap one ply of clear plastic wrap over the top of one of the shoeboxes. Tape the wrap around the edge to ensure the box is airtight. Place each box in direct sunlight, either on a windowsill or on a table outside, and start a stopwatch. Record the temperature in each box every five minutes for an hour before graphing your results. Your experiment will demonstrate the greenhouse effect, as the temperature in the box with plastic wrap rises faster and to a higher temperature than the one with no cover. Airtight plastic wrap keeps more of the sun's infrared rays within the shoebox.
Pour 1/2 cup vinegar, the acid, into an empty soda bottle. Stretch out the neck of a latex balloon before heaping 1 tbsp. bicarbonate of soda, the alkali, into the balloon. Stretch the balloon's neck over the neck of the soda bottle carefully so the bicarbonate of soda remains in the balloon and does not fall into the vinegar. Place the bottle in a sink and raise the balloon so the bicarbonate of soda falls in the vinegar. A violent reaction occurs between the acid and alkali, which inflate the balloon with carbon dioxide. This is because the vinegar's acetic acid reacts with the baking soda's sodium bicarbonate to form carbonic acid. This is unstable and falls apart into water and carbon dioxide.
Investigate the gas chemistry of lemonade. Assist any youngsters carrying out this project by slicing a lemon into quarters. Squeeze the juice into a drinking glass. Match the volume of lemon juice with the same amount of tap water. Stir the two together thoroughly using a metal spoon before tasting and writing down your observation about the flavor. Heap 1 tsp. baking soda into the drinking glass, stir vigorously and taste the mixture once more, noting your observations about the change the baking soda has made to the liquid, which is now fizzy. When an acid (lemon juice) and a base (baking soda) mix there is a process called "carbonization" as carbon dioxide is released. Using your taste test, add 1 tsp. sugar to sweeten if required.